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Thread: bitmaps in vb6

  1. #1
    Join Date
    Nov 2005

    bitmaps in vb6

    Hi all,
    I have a strange problem. The following code works very well. I copied it off of the net and although I would like to give credit where credit is due, there is no copyright notice or any id. The code returns a picturebox of a portion of the active screen. The problem is: I don't want a picturebox, I want a bitmap array I can process. more exactly, i need a bitmap and a handle to it, as in "c1 = GetPixel(bitmapHdl, x, y)".

    Now I am pretty sure that somewhere in this code is the bitmap and the handle to it I need, I just don't know which handle it is.

    I would like it very much if someone could tell me which handle it is.


    code follows:

    Public Type GUID
    Data1 As Long
    Data2 As Integer
    Data3 As Integer
    Data4(7) As Byte
    End Type

    Public Type PicBmp
    Size As Long
    Type As Long
    hBmp As Long
    hPal As Long
    Reserved As Long
    End Type

    Public Declare Function CreateCompatibleBitmap Lib "gdi32" ( _
    ByVal hdc As Long, ByVal nWidth As Long, _
    ByVal nHeight As Long) As Long

    Public Declare Function CreateCompatibleDC Lib "gdi32" ( _
    ByVal hdc As Long) As Long

    Public Declare Function BitBlt Lib "gdi32" ( _
    ByVal hDCDest As Long, ByVal XDest As Long, _
    ByVal YDest As Long, ByVal nWidth As Long, _
    ByVal nHeight As Long, ByVal hDCSrc As Long, _
    ByVal XSrc As Long, ByVal YSrc As Long, ByVal dwRop As Long) _
    As Long

    Public Declare Function GetForegroundWindow Lib "user32" () As Long

    Public Declare Function SelectObject Lib "gdi32" ( _
    ByVal hdc As Long, ByVal hObject As Long) As Long

    Public Declare Function OleCreatePictureIndirect _
    Lib "olepro32.dll" (PicDesc As PicBmp, RefIID As GUID, _
    ByVal fPictureOwnsHandle As Long, IPic As IPicture) As Long

    Public Function getBitmap(x As Integer, y As Integer, w As Integer, h As Integer) As Picture
    Dim hDCMemory As Long
    Dim hBmp As Long
    Dim hBmpPrev As Long
    Dim r As Long
    Dim hDCSrc As Long
    Dim hWndSrc As Long
    Dim Pic As PicBmp
    Dim IPic As IPicture
    Dim IID_IDispatch As GUID

    hWndSrc = GetForegroundWindow()
    hDCSrc = GetWindowDC(hWndSrc) 'Get DC for entire window.
    hDCMemory = CreateCompatibleDC(hDCSrc)
    hBmp = CreateCompatibleBitmap(hDCSrc, w, h)
    hBmpPrev = SelectObject(hDCMemory, hBmp)
    r = BitBlt(hDCMemory, 0, 0, w, h, hDCSrc, x, y, vbSrcCopy)
    hBmp = SelectObject(hDCMemory, hBmpPrev)
    r = DeleteDC(hDCMemory)
    r = ReleaseDC(hWndSrc, hDCSrc)
    With IID_IDispatch
    .Data1 = &H20400
    .Data4(0) = &HC0
    .Data4(7) = &H46
    End With
    With Pic
    .Size = Len(Pic) ' Length of structure
    .Type = vbPicTypeBitmap ' Type of Picture (bitmap)
    .hBmp = hBmp ' Handle to bitmap
    .hPal = 0 ' Handle to palette (may be null)
    End With
    r = OleCreatePictureIndirect(Pic, IID_IDispatch, 1, IPic)
    Set getBitmap = IPic
    End Function

  2. #2
    Join Date
    Nov 2003
    Alameda, CA
    use the Handle property of the StdPicture object to get back the handle of the bitmap, and then use the GetDIBBits API to get the image byte array from the bitmap
    You can also get back the bitmap handle directly (is the hbmp variable), but then you have to deal with releasing the memory yourself (something that right now is done automatically when the picture object goes out of scope)

    "There are two ways to write error-free programs. Only the third one works."

  3. #3
    Join Date
    Nov 2005

    bitmaps in vb6

    Hi Marco,

    Thank you for the tip. I spent several hours trying to get it to work without any luck. Although I did learn a lot. In the process I came across what I think may be a very good soultion for what I want. mainly to get rid of the picture boxes.

    Thanks again,
    **** roose

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